OAKLAND -- The oldest member of Vocal Rush at Oakland School for the Arts is just 18. But the ensemble of teenagers can bring a rowdy room to silence and tears to the eyes. Already they've won awards and applause and respect.

Now, on Monday, they will be singing for the top prize of $100,000 at the NBC "Sing-Off" finals. The top winner also gets a Sony recording contract.

The first song Vocal Rush performed during the competition was the gospel-influenced "Bottom of the River," with Jordan Holly, 18, as the lead vocalist.

Despite the darkly chilling lyrics -- "Hold my hand/Ooh, baby, it's a long way down to the bottom of the river" -- Vocal Rush impressed the judges with voices that seem impossibly masterful for teenagers, especially considering they sing a cappella.

Members of Vocal Rush, a singing troupe from Oakland School of the Arts, talk about their experience competing on NBC-TV's "Sing-Off," Tuesday, Dec. 17, 2013 in Oakland, Calif. (D. Ross Cameron/Bay Area News Group) (D. ROSS CAMERON)

It's just 10 girls, two boys and a lot of talent.

"We pushed ourselves as artists, not as teenagers," said Sydney Jacobs Allen, 17.

As Oakland School for the Arts vocalists, most of them already had several years of competing and performing experience before the "Sing-Off." The group had won several awards since its start as an after-school group in 2011, including twice at the International Championship of High School A Cappella. One of the soloists, Sarah Vela, won a Contemporary A Cappella Recording Award for Best High School Solo.

So they had high expectations of themselves from the start, said McKenna Lindell-Wright, 16. Their motto: "Age is just a number."

Still, the Sing-Off has been challenging because it is a TV competition broadcast to their families, friends and millions of viewers (7.8 million on Wednesday alone, according to Variety).

Performers must learn the songs quickly, interpret them convincingly and memorize the choreography while still worrying about homework.

Their second performance was the hip-hop favorite "Gonna make you sweat." Kyana Fanene had to beat-box the sound of a drum -- without sounding, as she put it, like an "electronic station" -- and stay in sync with the choreography.

Then they went voice to voice during a sing-off of the Destiny's Child hit "Survivor." The next day they had to out-sing the competition with the ballad "Against All Odds" to defend their place on the show.

"All the songs were outside our comfort zone," said Emma Stumpf, 17. "But that made it fun."

The competition involves vocal, mental and physical fatigue that requires stamina on and off the stage, said Kiana Parker, 18. They also had to learn to live together day in and day out.

"We know everything about each other," Lindell-Wright said.

They start each show by saying to each other, "I love you and I trust you."

They have been poised, articulate, and great artists, Vocal Rush Director Lisa Forkish said.

"OSA is just beyond proud."

The parents are also beyond proud. It was nerve-racking when they arrived at the competition in Los Angeles.

"But I knew they could bring it," said Andrea Mace-Hearne, mother of Jada Banks-Mace.

Monday will tell what the future has in store for them. It will not likely be a desk job.

Just 16, Banks-Mace summed up the way most of them feel about having come so far: "Music is not a safe route, but I'm not sure I can live without it."

"THE SING-OFF"

What: Vocal Rush, a 10-member group from Oakland School for the Arts, is among the finalists for the "Sing-Off," which showcases the country's top a cappella groups. The winning group will win $100,000 and a recording contract with Sony Music.When: 8-10 p.m. Monday Where: NBC Bay Area-KNTV